Heat oven to 325°F (160°F). Grease a 15 1/2 x 10 1/2 x 1-inch jelly roll pan with vegetable shortening or butter. Line bottom of pan with parchment paper. Set aside. For cake, place the 18 ounces chocolate in medium microwave proof bowl. Cover with plastic wrap, turning back one corner to vent. Microwave on High 1 1/2 minutes; stir and microwave 30 to 45 seconds more, until chocolate is melted and completely smooth. Keep chocolate covered so it remains warm. Beat egg yolks, butter, almond flour (if using whole blanched almonds, process nuts with 2 tablespoons of the sugar in food processor until finely ground) and corn syrup in large mixer bowl on medium-high speed, until light and fluffy. Beat in rum, if desired. Beat egg whites in a clean mixer bowl with clean beaters on medium speed, until foamy. Beat in sugar (or remaining 10 tablespoons sugar, if using whole blanched almonds) 1 tablespoon at a time. Increase speed to medium-high and beat to stiff peaks. Gently fold whites into almond mixture with a rubber spatula, until almost combined. Gently fold in the warm chocolate, until well combined. Spread batter into prepared pan. Bake cake 30 to 35 minutes, until top springs back when lightly touched and a toothpick inserted in center comes out clean. Cool cake completely on wire rack. For Truffle Ganache, line the bottom of another 15 1/2 x 10 1/2 x 1-inch jelly roll pan with parchment paper. Set aside. Heat heavy cream in medium saucepan over medium heat, until bubbles begin to form around edge of pan. Place the 21 ounces chocolate in medium bowl and pour half of the hot cream over chocolate. Whisk chocolate slowly until smooth. Gradually add remaining hot cream, whisking until chocolate is completely smooth. Stir in orange-flavored liqueur, if desired, or orange peel. Pour ganache into prepared pan. Let stand at room temperature until ganache is cool and spreadable (the consistency of icing), about 45 to 60 minutes. Makes about 3 3/4 cups. Carefully invert cake onto a cutting board lined with parchment or waxed paper. Peel off parchment from bottom of cake. Trim 1/4-inch from edges of cake. Cut cake crosswise into three 5 x 10-inch pieces. With long, flat spatula, lift one piece onto a flat serving platter. Spread 3/4 cup of ganache over top. Repeat layering two more times. Frost sides with 1/2 cup ganache, keeping sides and top as smooth as possible. Refrigerate cake until ganache becomes firm, 15 to 20 minutes. Fill a large pastry bag fitted with #2 round tip with the remaining 1 cup ganache. Decoratively pipe ganache along top and bottom edge of cake (or use the tines of a fork to draw lines along the cake). Garnish cake with raspberries and mint sprigs, if desired.